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Chapter 22
LCD Controller/Driver (LCD-C/D)
Preliminary User’s Manual U17566EE1V2UM00
22.3 Operation
The following describes the timing of common and segment signals, the
activation of an LCD segment and how edge enhancement can be applied.
22.3.1
Common signals and segment signals
This section describes the timing of common signals and segment signals and
at which conditions an individual LCD segment becomes visible.
(1)
Common Signals
Common signals COM0 to COM3 are generated internally. Together with the
segment signals, they define which LCD segment is activated in the current
cycle.
Figure 22-3
shows the common signal wave form for COM0, 1/4 duty (1/3
bias). 1/4 duty means each signal COMn is in selection level for one quarter of
a frame.
Figure 22-3
Common signal wave form (1/4 duty, 1/3 bias)
• T
F
= frame cycle time.
T
F
= 4 x T
T corresponds to the duty cycle frequency f
LCD1
and is thus determined by
register LCDC.
• T = duty cycle time.
Each frame cycle T
F
is comprised of 4 duty cycles (1/4 duty), one duty cycle
for each signal COMn.
Each LCD segment is allocated to one of the common signals. The LCD
segment can only be activated in a duty cycle, in which the common signal is
at selection level.
Figure 22-4
shows the selection and non-selection level of common signals.
Figure 22-4
Selection level and non-selection level of common signals
T = duty cycle time.
T
F
= 4 x T
COM0
(Divided by 4)
V
LC0
V
SS1
V
LCD
V
LC1
V
LC2
S
elected
Not
s
elected
Common
s
ign
a
l
V
LC0
V
SS
1
V
LCD
V
LC2
V
LC1
T
T
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